Add .editorconfig to project for consistency

#### What's the plan?
Add our .editorconfig to project for consistency.

#### What's this PR do?
Adds our .editorconfig file.

#### How should this be manually tested?

#### What are the relevant tickets?
n/a

#### Next steps?

#### Smells?

#### TODOs:

#### Has the relevant documentation/wiki been updated?
Added to README.

#### Technical debt note